We have employed several systems to investigate the problem of control of biological function at the molecular level in animal cells. For this purpose we have been interested in virus replication and its inhibition since these can be studied at the molecular level. Early functions of an oncogenic virus, SV40, which seem in relation to tumor induction are under study. In the case of interferon, a natural inhibition of virus growth, we have studied murine leukemia virus production in interferon-treated cells. We have also been interested in alterations in plasma membranes induced by interferon treatment in interferon binding sites on the cell surface. Finally, we are examining the role of interferon in the induction and persistence of chronic viral infections. BIBLIOGRAPHIC REFERENCES: Chang, E.H., Mims, S.J., Triche, T.J., Friedman, R.M. Interferon inhibits mouse leukemia virus release: An electron microscope study. J. Gen. Virol. 34, 363, 1977. Chang, E.H., Myers, M.W., Wong, P.K.Y., and Friedman, R.M. The inhibitory effect of interferon on a temperature-sensitive mutant of Moloney murine leukemia virus. Virology 77: 625, 1977.